Many modern motor vehicles including vans, minivans, SUVs, etc. have sliding side doors and sometimes rear liftgates or hatch-back doors as well. As used herein, the term “door” is understood to collectively encompass slideable doors, pivotable liftgates, pivotable tailgates, and pivotable hatchbacks. When closed, these doors fit against a vehicle door frame. These doors can be rather heavy and develop inertia as they move. As such, should an object be caught between a closing door and the vehicle door frame, damage can occur to the object (which may be a person), to the door and/or to the vehicle door frame. While opening, many side doors first move outward, away from the vehicle body, before moving rearward, and can cause damage to an object thus contacted. A liftgate, tailgate, or hatchback can strike an object while opening or closing, even if an object is not close to the associated vehicle door frame. As used herein, the term “contact zone” is understood to refer to region or zone of interest in which an object may be contacted by a moving door. As such, the contact zone includes the path and/or trajectory of the moving door. In some embodiments, the contact zone is defined relative to the position of the door and thus moves as the door moves, and indeed, in some embodiments the dimensions of the contact zone may vary with at least one door parameter, for example, present door position and present door velocity.
In many vehicles, doors are opened or closed using motors controlled by the vehicle operator from a remote location, e.g., the driver's seat. A practical problem is that the vehicle operator cannot always see what if any object(s) are in the contact zone. As a result, damage to the object and/or door and/or associated vehicle door frame can occur before meaningful remedial action can be taken, e.g., to reverse or halt movement of the door.
In an attempt to reduce likelihood of damage from contact between a moving vehicle door and an object, the federal government has mandated Federal Motor Vehicle Safety Standard 118. This standard calls for implementation of so-called anti-pinch devices that sense contact when an object is between a closing vehicle door and the associated vehicle door frame. Some anti-pinch devices are contact devices that require physical contact with an object and the vehicle door and/or door frame, whereas other anti-pinch devise are contactless, and do not require such contact.
Contact type anti-pinch devices try to mitigate damage after initial contact between an object and the vehicle door and/or door frame occurs. As soon as contact is detected, a control signal is generated causing the motor moving the door to halt or to reverse direction. Some contact sensors dispose a tube or trim within the relevant vehicle door frame region, and then sense at least one contact-caused parameter such as pressure, capacitance change, optical change, electrical current increase in the door drive motor, etc. The tube or trim may contain spaced-apart electrical wires that make contact only if an object depresses the tube or trim. In practice, such sensors are sometimes difficult to install, and can exhibit varying contact responses, especially as ambient temperature changes. But even if the best contact type anti-pinch device can only begin to function after some physical contact with an object has first occurred. Thus, a corrective command signal is not issued until initial contact occurs. In some instances, corrective action may come too late. For example, upon detecting contact there may be insufficient time to fully halt the closing action of a sliding door on a vehicle parked on a steep downhill incline. An object, which may be a person's hand, could be severely damaged before the closing inertia of the sliding door can be halted.
By contrast, an ideal contactless anti-pinch device would prevent contact damage by detecting the presence of an object within a contact zone and taking immediate corrective action without first requiring initial contact.
Various attempts have been made in the prior art to implement a contactless anti-pinch device, at least with respect to a human object. One such approach seeks to detect microampere range electrical current changes resulting from capacitance in the skin of a human object. Electrical sensors disposed in regions of the vehicle door frame and/or door allegedly can thus contactlessly sense the presence of human objects by such capacitance and/or current changes. Whether such sensors can detect human proximity to a closing door under varying ambient parameters is unknown to applicants. But even if such devices worked flawlessly, and there is no evidence such is the case, passive objects such as tree limbs, other vehicles, or non-exposed human skin such as gloved hands, do not manifest skin capacitance responsive to current (or voltage) change, and thus would go undetected.
In theory, other approaches to contactless sensing might include use of conventional television-type cameras to image the contact zones. However in practice, the images produced by such cameras lack useful depth information and would not adequately identify objects in the contact zone such that remedial action could be undertaken. Approaches such as attempting to identify human objects in the contact zone using infrared (IR) sensors would similarly not work well, especially at high ambient temperatures. Further, such IR sensing would be of little use as to objects that did not generate heat. Object sensing using ultra sound would lack adequate resolution and spatial coverage.
A more promising technology for contactless sensing is true three-dimensional cameras that can form a Z or depth image of an object. Canesta, Inc., of Sunnyvale, Calif., assignee herein, has developed various time-of-flight (TOF) systems. Various aspects of TOF imaging systems are described in the following patents assigned to Canesta, Inc.: U.S. Pat. No. 6,323,942 entitled “CMOS-Compatible Three-Dimensional Image Sensor IC”, U.S. Pat. No. 7,203,356 “Subject Segmentation and Tracking Using 3D Sensing Technology for Video Compression in Multimedia Applications”, U.S. Pat. No. 6,906,793 Methods and Devices for Charge Management for Three-Dimensional Sensing”, and U.S. Pat. No. 6,580,496 “Systems for CMOS-Compatible Three-Dimensional Image Sensing Using Quantum Efficiency Modulation”, U.S. Pat. No. 6,515,740 “Methods for CMOS-Compatible Three-Dimensional image Sensing Using Quantum Efficiency Modulation”. Applicants refer to and incorporate herein by reference the above-enumerated patents for background material.
FIG. 1 depicts an exemplary TOF system, as described in Canesta U.S. Pat. No. 6,323,942. TOF system 10 can be implemented on a single IC 110, without moving parts, preferably with relatively few off-chip components. System 100 includes a two-dimensional array 130 of Z pixel detectors 140, each of which has dedicated circuitry 150 for processing detection charge output by the associated detector. In a typical application, array 130 might include 100×100 pixels 140, and thus include 100×100 processing circuits 150. IC 110 preferably also includes a microprocessor or microcontroller unit 160, memory 170 (which preferably includes random access memory or RAM and read-only memory or ROM), a high speed distributable clock 180, and various computing and input/output (I/O) circuitry 190. Among other functions, controller unit 160 may perform distance to object and object velocity calculations, which may be output as DATA.
Under control of microprocessor 160, a source of optical energy 120, typical IR or NIR wavelengths, is periodically energized and emits optical energy S1 via lens 125 toward an object 20. Typically the optical energy is light, for example emitted by a laser diode or LED device 120. Some of the emitted optical energy will be reflected off the surface of target object 20 as reflected energy S2. This reflected energy passes through an aperture field stop and lens, collectively 135, and will fall upon two-dimensional array 130 of pixel detectors 140 where a depth or Z image is formed. In some implementations, each imaging pixel detector 140 captures time-of-flight (TOF) required for optical energy transmitted by emitter 120 to reach target object 20 and be reflected back for detection by two-dimensional sensor array 130. Using this TOF information, distances Z can be determined as part of the DATA signal that can be output elsewhere, as needed.
Emitted optical energy S1 traversing to more distant surface regions of target object 20, e.g., Z3, before being reflected back toward system 100 will define a longer time-of-flight than radiation falling upon and being reflected from a nearer surface portion of the target object (or a closer target object), e.g., at distance Z1. For example the time-of-flight for optical energy to traverse the roundtrip path noted at t1 is given by t1=2·Z1/C, where C is velocity of light. TOF sensor system 10 can acquire three-dimensional images of a target object in real time, simultaneously acquiring both luminosity data (e.g., signal brightness amplitude) and true TOF distance (Z) measurements of a target object or scene.
Many Canesta, Inc. systems determine TOF and construct a depth image by examining relative phase shift between the transmitted light signals S1 having a known phase, and signals S2 reflected from the target object. Exemplary such phase-type TOF systems are described in several U.S. patents assigned to Canesta, Inc., assignee herein, including U.S. Pat. No. 6,515,740 “Methods for CMOS-Compatible Three-Dimensional Imaging Sensing Using Quantum Efficiency Modulation”, U.S. Pat. No. 6,906,793 entitled Methods and Devices for Charge Management for Three Dimensional Sensing, U.S. Pat. No. 6,678,039 “Method and System to Enhance Dynamic Range Conversion Useable With CMOS Three-Dimensional Imaging”, U.S. Pat. No. 6,587,186 “CMOS-Compatible Three-Dimensional Image Sensing Using Reduced Peak Energy”, and U.S. Pat. No. 6,580,496 “Systems for CMOS-Compatible Three-Dimensional Image Sensing Using Quantum Efficiency Modulation”. Applicants refer to and incorporate hereby by reference these above-enumerated patents for further background material.
FIG. 2A is based upon above-noted U.S. Pat. No. 6,906,793 and depicts an exemplary phase-type TOF system in which phase shift between emitted and detected signals, respectively, S1 and S2 provides a measure of distance Z to target object 20. Under control of microprocessor 160, optical energy source 120 is periodically energized by an exciter 115, and emits output modulated optical energy S1=Sout=cos(ωt) having a known phase towards object 20. Emitter 120 preferably is at least one LED or laser diode(s) emitting low power (e.g., perhaps 1 W) periodic waveform, producing optical energy emissions of known frequency (perhaps a few dozen MHz) for a time period known as the shutter time (perhaps 10 ms).
Some of the emitted optical energy (denoted Sout) will be reflected (denoted S2=Sin) off the surface of target object 20, and will pass through aperture field stop and lens, collectively 135, and will fall upon two-dimensional array 130 of pixel or photodetectors 140. When reflected optical energy Sin impinges upon photodetectors 140 in array 130, photons within the photodetectors are released, and converted into tiny amounts of detection current. For ease of explanation, incoming optical energy may be modeled as Sin=A·cos(ω·t+θ), where A is a brightness or intensity coefficient, ω·t represents the periodic modulation frequency, and θ is phase shift. Thus, array 130 captures frames of Z depth and brightness data, typically at a frame rate of perhaps 30 to 60 frames/second. While the scene and object within are imaged with the same modulated optical energy Sout, each pixel detector 140 in array 130 will receive an object-reflected signal with a different delay (θ) that corresponds to the varying z depth of the surface of the imaged object within the system field of view (FOV).
As distance Z changes, phase shift θ changes, and FIGS. 2B and 2C depict a phase shift θ between emitted and detected signals, S1, S2. The phase shift θ data can be processed to yield desired Z depth information. Within array 130, pixel detection current can be integrated to accumulate a meaningful detection signal, used to form a depth image. In this fashion, TOF system 100 can capture and provide Z depth information at each pixel detector 140 in sensor array 130 for each frame of acquired data. In some systems, pixel detection information is captured at at least two discrete phases, preferably 0° and 90°, and is processed to yield Z data. System 100 yields a phase shift θ at distance Z due to time-of-flight given by θ=2·ω·Z/C=2·(2·π f)·Z/C, where C is the speed of light, 300,000 Km/sec. From the above equation, it follows that distance Z is given by Z=θ·C/2·ω=θ·C/(2·2·f·π). When θ=2·π, the aliasing interval range associated with modulation frequency f is given as Z=C/(2·f). In practice, changes in Z produce change in phase shift θ although eventually the phase shift begins to repeat, e.g., θ=θ+2·π, etc. Thus, distance Z is known modulo 2·π·C/2·ω)=C/2·f, where f is the modulation frequency.
What is needed is a contactless anti-pinch method and system for use with motor vehicles that can identify an object in the contact zone in adequate time to take remedial action to mitigate against physical contact between the object and the vehicle door or door frame. Preferably the method and system should be operable under widely varying conditions such as changes in ambient lighting. Indeed, ideally the method and system should operate even in the absence of ambient light. Finally, the method and system should be economically mass producible and readily installable.
The present invention provides such protective mechanisms and methods to detect objects in the contact zone or trajectory path of remotely controllably power doors.